Show selected subform items in a table field

[krazieddi]

given a subform that lists items:

a
b
c
d
e
f
g

given a table that contains a coverage field

customer coverage
smith a, b, d, g


how would i create a relationship bewteen a subform and a coverage field such that when i multi select items in the subform, it will show what items are selected in the coverage field as in the example

 

[Uncle Gizmo]

>>>>such that when i multi select items in the subform, <<<<

Where are you saving the selections?